From 7488d6d3679829b67a7fac394340d629f667ab15 Mon Sep 17 00:00:00 2001
From: John Stewien <stewienj@users.noreply.github.com>
Date: Thu, 17 Aug 2017 17:07:21 +0930
Subject: [PATCH] AvalonDock fixed tabs undocking when changing tabs to a
 different sized tab, related to AutoSize setting.

---
 .../Controls/LayoutAnchorableTabItem.cs       | 26 ++++++++++++++++---
 .../Layout/LayoutContent.cs                   |  1 +
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/ExtendedWPFToolkitSolution/Src/Xceed.Wpf.AvalonDock/Controls/LayoutAnchorableTabItem.cs b/ExtendedWPFToolkitSolution/Src/Xceed.Wpf.AvalonDock/Controls/LayoutAnchorableTabItem.cs
index ee6695d7..856260cf 100644
--- a/ExtendedWPFToolkitSolution/Src/Xceed.Wpf.AvalonDock/Controls/LayoutAnchorableTabItem.cs
+++ b/ExtendedWPFToolkitSolution/Src/Xceed.Wpf.AvalonDock/Controls/LayoutAnchorableTabItem.cs
@@ -116,8 +116,11 @@ namespace Xceed.Wpf.AvalonDock.Controls
 
         #endregion
 
-        bool _isMouseDown = false;
-        static LayoutAnchorableTabItem _draggingItem = null;
+        private bool _isMouseDown = false;
+        private static LayoutAnchorableTabItem _draggingItem = null;
+        // There's an issue with panes resizing when selecting another tab, causing a
+        // mouse leave event to make the tab undock. This fixes that.
+        private static bool _cancelNextMouseLeave = false;
 
         internal static bool IsDraggingItem()
         {
@@ -132,6 +135,10 @@ namespace Xceed.Wpf.AvalonDock.Controls
         {
             _draggingItem = null;
         }
+        internal static void CancelNextMouseLeave()
+        {
+            _cancelNextMouseLeave = true;
+        }
 
         protected override void OnMouseLeftButtonDown(System.Windows.Input.MouseButtonEventArgs e)
         {
@@ -150,6 +157,11 @@ namespace Xceed.Wpf.AvalonDock.Controls
                 _isMouseDown = false;
                 _draggingItem = null;
             }
+            else
+            {
+                _cancelNextMouseLeave = false;
+            }
+
         }
 
         protected override void OnMouseLeftButtonUp(System.Windows.Input.MouseButtonEventArgs e)
@@ -167,10 +179,18 @@ namespace Xceed.Wpf.AvalonDock.Controls
 
             if (_isMouseDown && e.LeftButton == MouseButtonState.Pressed)
             {
-                _draggingItem = this;
+                if (!_cancelNextMouseLeave)
+                {
+                    _draggingItem = this;
+                }
+                else
+                {
+                    _draggingItem = null;
+                }
             }
 
             _isMouseDown = false;
+            _cancelNextMouseLeave = false;
         }
 
         protected override void OnMouseEnter(MouseEventArgs e)
diff --git a/ExtendedWPFToolkitSolution/Src/Xceed.Wpf.AvalonDock/Layout/LayoutContent.cs b/ExtendedWPFToolkitSolution/Src/Xceed.Wpf.AvalonDock/Layout/LayoutContent.cs
index d7b3eaba..b65cf913 100644
--- a/ExtendedWPFToolkitSolution/Src/Xceed.Wpf.AvalonDock/Layout/LayoutContent.cs
+++ b/ExtendedWPFToolkitSolution/Src/Xceed.Wpf.AvalonDock/Layout/LayoutContent.cs
@@ -127,6 +127,7 @@ namespace Xceed.Wpf.AvalonDock.Layout
                         parentSelector.SelectedContentIndex = _isSelected ? parentSelector.IndexOf(this) : -1;
                     OnIsSelectedChanged(oldValue, value);
                     RaisePropertyChanged("IsSelected");
+                    Controls.LayoutAnchorableTabItem.CancelNextMouseLeave();
                 }
             }
         }